Closed-cell polyisocyanate-based foams are widely used for insulation purposes, for example, in building construction and in the manufacture of energy efficient electrical appliances. In the construction industry, polyurethane/polyisocyanurate board stock is used in roofing and siding for its insulation and load-carrying capabilities. Poured and sprayed polyurethane foams are widely used for a variety of applications including insulating roofs, insulating large structures such as storage tanks, insulating appliances such as refrigerators and freezers, insulating refrigerated trucks and railcars, etc.
All of these various types of polyurethane/polyisocyanurate foams require blowing agents for their manufacture. Insulating foams depend on the use of halocarbon blowing agents, not only to foam the polymer, but primarily for their low vapor thermal conductivity, a very important characteristic for insulation value. Historically, polyurethane foams used CFCs (chlorofluorocarbons, for example CFC-11, trichlorofluoromethane) and HCFCs (hydrochlorofluorocarbons, for example HCFC-141b, 1,1-dichloro-1-fluoroethane) as the primary blowing agent. However, due to the implication of chlorine-containing molecules such as the CFCs and HCFCs in the destruction of stratospheric ozone, the production and use of CFCs and HCFCs has been restricted by the Montreal Protocol. More recently, hydrofluorocarbons (HFCs), which do not contribute to the destruction of stratospheric ozone, have been employed as blowing agents for polyurethane foams. An example of an HFC employed in this application is HFC-245fa (1,1,1,3,3-pentafluoropropane). The HFCs do not contribute to the destruction of stratospheric ozone, but are of concern due to their contribution to the “greenhouse effect”, i.e., they contribute to global warming. As a result of their contribution to global warming, the HFCs have come under scrutiny, and their widespread use may also be limited in the future.
Hydrocarbons have also been proposed as foam blowing agents. However, these compounds are flammable, and many are photochemically reactive, and as a result contribute to the production of ground level ozone (i.e., smog). Such compounds are typically referred to as volatile organic compounds (VOCs), and are subject to environmental regulations.
There is need for producing foams that provide low flammability, good thermal insulation and high dimensional stability by using a blowing agent that has substantially no ozone depletion potential (ODP) and no or very low global warming potential (GWP). Cis-1,1,1,4,4,4-hexafluoro-2-butene (Z-FC-1336mzz, or Z—CF3CH═CHCF3) is one of the good candidates.
Japanese Patent No. 05179043 discloses and attempts to use cis-1,1,1,4,4,4-hexafluoro-2-butene as the blowing agent for polyurethane foams.